Power control system and method

ABSTRACT

This invention discloses a power control system comprising a prime mover and a generator driven by the prime mover. A control device is coupled with the generator to ascertain a change in speed of the generator and vary an output power of the generator according to the change. The control device applies a signal to reduce the generator output power and another signal to restore the generator output power. The power control system may include a transmission, a speed converter, and/or an accessory.

CROSS REFERENCE TO RELATED APPLICATIONS

The present patent application is a division of a co-pendingnon-provisional patent application entitled “POWER CONTROL SYSTEM ANDMETHOD,” filed Apr. 3, 2006, as U.S. patent application Ser. No.11/397,523 by the same inventors. This patent application claims thebenefit of the filing date of the cited non-provisional patentapplication according to the statutes and rules governingnon-provisional patent applications, particularly 35 USC §§120, 121, and37 CFR §1.78. The specification and drawings of the citednon-provisional patent application are specifically incorporated hereinby reference.

COPYRIGHT

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The owner has no objection tothe facsimile reproduction by anyone of the patent disclosure, as itappears in the Patent and Trademark Office files or records, butotherwise reserves all copyright rights whatsoever.

FIELD OF INVENTION

This invention is related to power control systems comprising a primemover, such as an internal combustion engine, and a generator driven bythe prime mover. In particular, this invention relates to a controldevice, including a system and method, which controls the output powerof the generator according to a change in speed of the generator or theprime mover by measuring a speed of a generator or prime mover speedindicator and varying the output power of the generator according tosaid change.

BACKGROUND

The present invention relates to power control systems which comprise aprime mover and a generator driven by the prime mover. Such a powersystem may be implemented in a vehicle, where an internal combustionengine provides mechanical power to propel the vehicle, and to driveengine accessories, such as generators, air conditioning units,compressors, cooling fans, and pumps, to name a few examples. In agenerator set, an internal combustion engine drives a generator toconvert the engine's mechanical power into electrical power. The presentinvention specifically focuses on a control device that controls thegenerator output power in order to avoid excessive load on the engineand the drive components. In particular, the control device isconfigured to ascertain a change in speed of the generator or the engineand to control the generator output power controller to avoid stallingthe engine.

Electro-mechanical power conversion systems, such as those mentionedabove, are normally comprised of an internal combustion engine and agenerator. The engine supplies the generator with mechanical power whereit is converted to electrical power. In a vehicle, for instance, thegenerator generates electrical power for the vehicle electrical systemwhen the vehicle's engine is operating. In a generator set, the engine'smechanical power is converted to electrical power by the generator whichis available via power output connectors. As electrical loads are addedand removed from the generator, the engine experiences the correspondingvariation in mechanical loads. In the case of the vehicle, during idleperiods, such variations in mechanical loads on the engine cause theengine's rotational speed, commonly referred to as the RPM (revolutionper minute) to vary accordingly. In the case of the generator set,similar changes in the RPM occur as electrical loads are connected anddisconnected with the power output connectors.

The engine drives the generator, via a coupling, at a substantiallyequivalent speed. A typical coupling between an engine and a generatorcomprises a pair of pulleys and one or more belts that are used toimpart the engine's speed onto the generator. Another type of couplinginvolves splined shafts where specially machined shafts of the engineand generator are mated together so that the engine's shaft directlydrives the generator's shaft.

Engine stall is a common problem in electromechanical power conversionsystems, such as those mentioned above. Engine stalls when there isexcessive mechanical power demand on the engine. This demand can be dueto electrical loads on the generator or any other mechanical powerconsuming device driven by the engine. A typical internal combustionengine power output is a function of the engine RPM. At steady stateconditions, the engine can deliver a certain torque at the operatingRPM. As the torque requirement exceeds this torque the engine RPM beginsto decrease which may eventually cause the engine to stall. In addition,a rapid change in the power transfer, can damage the drive mechanism.

Furthermore, sudden power demand from the engine can be hindered by theexisting mechanical loads on the engine. Such mechanical loads can bedue to a generator and/or an accessory, such as an electrical motor. Themechanical load on the engine, due to the generator, can be excessive.Removal or attenuation of such load from the engine can supply theengine with the power it needs to meet the sudden power demand.

Although various systems have been proposed which touch upon someaspects of the above problems, they do not provide solutions to theexisting limitations in power control systems. For example, inBlackburn, U.S. Pat. No. 6,801,020, the invention is directed to amethod of limiting a rate of change of the output current supplied by astarter/alternator in the generator mode, thereby limiting thepossibility that the rapidly increasing electrical load could eitherstall or cause another operational fault in the associated internalcombustion engine. The present invention focuses on a change in thespeed of the generator and controls its output according to the change.Accordingly, any change in speed, regardless of the source that causedsuch change, will be monitored and acted upon.

In Fenley, U.S. Pat. No. 5,570,001, the invention discloses an apparatusthat includes an engine driving an alternator where the engine speed isautomatically controlled by manipulating the throttle according to thecharging current of the alternator. The apparatus is further capable ofunloading the alternator from the engine when excessive electrical loadsare engaged, in order to prevent the engine from stalling. However,since this apparatus operates on detecting the alternator current, it isprone to electrical noise. The system described herein monitors a changein speed which is a mechanical action rather than monitoring anelectrical variable. Furthermore, electric current at a fixed voltage isrelated to electric power which in turn is related to the mechanicalpower produced by the engine. That is why Fenley teaches unloading thealternator at an excessive current. But the engine mechanical powervaries also with combustion air density, fuel energy content, ambienttemperature, wear condition of the engine, other parasitic loads drivenby the engine, and various other conditions that Fenley needs toconsider in calibrating engine overload power. The system describedherein does not need to consider such influences to the available enginepower because a sudden reduction of engine speed is presumed to be anoverload on the engine power, no matter the source of that overload.

In DeBiasi et al., U.S. Pat. No. 5,481,176, the disclosure describes acharging system including an engine driving an alternator and a voltageregulator, where the voltage regulator voltage set-point is modified byan engine controller device according to (1) near-wide-open-throttle,(2) application of vehicle brakes, and (3) increased torque of thealternator, or any combination thereof. When condition (3) is met, theengine controller manipulates the engine idle speed to keep itrelatively constant as the applied electrical loads cause thealternator's torque on the engine to increase. However, this chargingsystem monitors an increase in alternator torque on the engine, whereasthe present invention monitors a change in the rotational speed of thealternator. Additionally, the DeBiasi system responds to an increase intorque of the alternator on the engine, whereas the present inventionresponds to a change in torque on the engine regardless of the source,even torque changes from an accessory other than the alternator that isdriven by the engine.

In a copending commonly assigned U.S. patent application Ser. No.11/234,579, filed Sep. 23, 2005 and entitled “Power Control System andMethod,” hereby incorporated by reference in its entirety, a powercontrol system was disclosed where a control device ascertained a powerlevel of the generator and varied an output power of the prime moveraccording to the power level. More specifically, the prime mover outputpower was manipulated so that the generator power level could bemaintained within a specified range. The present invention complementsthis system by providing an additional protection to the engine fromstalling during those periods when the change in engine rotational speedis so high that a faster response than manipulating the engine's outputpower is required.

Power conversion systems, such as those incorporated in a vehicle or agenerator set, utilize a prime mover and a generator. The output powerof the prime mover may be adjusted in accordance with the power level ofthe generator. Additional protection can be afforded such systems bymonitoring the change in the rotational speed of the generator or theprime mover and manipulating the output power of the generator to avoidexcessive loads on the engine. Where a situation arises that the primemover output power adjustment does not adequately address the excessiveload problem of such prime movers, the present invention provides anadditional protection by adjusting the output power of the generator.

SUMMARY

The present invention discloses a control device, including a system andmethod, which can be utilized in a power conversion system to ensureefficient power conversion and improved operation. The power conversionsystem includes a prime mover, such as an internal combustion engine,and a generator, such as an alternator, that is driven by the primemover. The control device is coupled with the generator, and itascertains a change in speed of the generator and varies an output powerof the generator according to the change. Preferably, the control deviceis coupled with the generator via a generator output power controller,capable of manipulating an output power of the generator. The controldevice is configured to measure a change in speed of the generator, viaa generator speed indicator and to apply a control signal to thegenerator output power controller according to the change. The controldevice may be further configured to regulate an output voltage of thegenerator via the generator output power controller. The power controlsystem may include a transmission, a speed converter, and/or anaccessory. The control device may be further configured to communicatesystem information to a computer system.

In one aspect, a power control system is disclosed comprising a primemover, a generator, and a control device connected to and incommunication with the generator. The control device is configured toascertain a change in speed of the generator and to vary an output powerof the generator according to said change. Preferably, the generatorcomprises a generator output power controller and a speed indicatorcoupled with the control device and wherein the control deviceascertains a change in speed of the generator via said speed indicatorand varies an output power of the generator by applying a control signalto the generator output power controller according to the change.Preferably, the control device either reduces or restores the generatoroutput power when the change is above a threshold value. In oneinstance, the control device reduces the generator output power when thespeed is decreasing, i.e., the algebraic sign of the change is negativeand restores the generator output power when the speed is increasing,i.e., the algebraic sign of the change is positive.

In another aspect, a power control system is disclosed comprising aprime mover, a generator, and a control device connected to and incommunication with the generator. The control device is configured toascertain a change in speed of the generator and to vary an output powerof the generator according to said change. Preferably, the controldevice further comprises a voltage regulator capable of regulating theoutput voltage of the generator at a regulation voltage. Preferably, thecontrol device varies the regulation voltage according to the change,hence, it either reduces or restores the regulation voltage when thechange is above a threshold value. In one instance, the control devicereduces the regulation voltage when the speed is decreasing, i.e., thealgebraic sign of the change is negative and restores the regulationvoltage when the speed is increasing, i.e., the algebraic sign of thechange is positive.

In another aspect, a power control system is disclosed comprising aprime mover, a generator, and a control device connected to and incommunication with the generator. The control device is configured toascertain a change in speed of the generator and to vary an output powerof the generator according to said change. Preferably, the power controlsystem further includes communication means in order to provide systeminformation. Preferably, the control device comprises visual indicators,such as light emitting diodes (LEDs) which generate flashing lightpatterns indicative of said system information. The control device mayfurther incorporate a communication port where the system information iscommunicated to a computer system.

In another aspect, a power control system is disclosed comprising aprime mover, a generator, and a control device connected to and incommunication with the generator. The control device is configured toascertain a change in speed of the generator and to vary an output powerof the generator according to said change. Preferably, the controldevice comprises a processor coupled with the generator output powercontroller and speed indicator wherein the processor measures a changein speed of the generator, via a first line, and varies the output powerof the generator by applying a speed-control signal to the generatoroutput power controller, via a second line, according to the change. Inone instance, the generator speed indicator is a phase winding of thegenerator, wherein the processor ascertains a change in generator RPM,via the first line, and the generator output power controller is agenerator field coil, wherein the processor applies a speed-controlsignal to vary the generator output power, via the second line.Preferably, the processor is configured to apply either a phasemodulated signal or a step signal when the change is above a thresholdvalue. In one instance, the processor is configured to apply a phasemodulated signal when the speed is decreasing, i.e., the algebraic signof the change is negative and to apply a step signal when the speed isincreasing, i.e., the algebraic sign of the change is positive.

In another aspect, a power control system is disclosed comprising aprime mover, a generator, and a control device connected to and incommunication with the generator. The control device is configured toascertain a change in speed of the generator and to vary an output powerof the generator according to said change. Preferably, the controldevice comprises a processor coupled with the generator output powercontroller and speed indicator wherein the processor measures a changein speed of the generator, via a first line, and varies the output powerof the generator by applying a speed-control signal to the generatoroutput power controller, via a second line, according to the change.Preferably the processor is further coupled with an output terminal ofthe generator and configured to measure an output voltage of thegenerator, via a third line, and to apply a voltage-control signal tothe generator output power controller, via a fourth line, so that theoutput voltage is maintained at a regulation voltage. In one instance,the processor is configured to apply only a voltage-control signal tothe generator output power controller, via the second line, wherein theregulation voltage is varied according to the change, thus eliminatingthe need for the fourth line. Preferably, the processor varies theregulation voltage according to the change, hence, it either reduces orrestores the regulation voltage when the change is above a thresholdvalue. In one instance, the processor reduces the regulation voltagewhen the speed is decreasing, i.e., the algebraic sign of the change isnegative and restores the regulation voltage when the speed isincreasing, i.e., the algebraic sign of the change is positive.

In one aspect, a method is disclosed for controlling a power controlsystem comprising a prime mover and a generator driven by the primemover. The method comprises ascertaining a change in speed of thegenerator, via a generator speed indicator, and varying an output powerof the generator, via a generator output power controller, according tosaid change. Preferably, the method comprises either reducing orrestoring the generator output power when the change is above athreshold value. In one instance, the method comprises reducing thegenerator output power when the speed is decreasing, i.e., the algebraicsign of the change is negative and restoring the generator output powerwhen the speed is increasing, i.e., the algebraic sign of the change ispositive.

In one aspect, a method is disclosed for controlling a power controlsystem comprising a prime mover and a generator driven by the primemover. The method comprises ascertaining a change in speed of thegenerator, via a generator speed indicator, and varying an output powerof the generator, via a generator output power controller, according tosaid change. Preferably, the method further comprises maintaining anoutput voltage of the generator, via a voltage regulator, at aregulation voltage. Preferably, the method comprises varying theregulation voltage according to the change, hence, either reducing orrestoring the regulation voltage when the change is above a thresholdvalue. In one instance, the method comprises reducing the regulationvoltage when the speed is decreasing, i.e., the algebraic sign of thechange is negative and restoring the regulation voltage when the speedis increasing, i.e., the algebraic sign of the change is positive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of a power control system according to apreferred embodiment.

FIG. 2 shows a block diagram of a power control system according to apreferred embodiment.

FIG. 3 shows a block diagram of a power control system according to apreferred embodiment.

FIG. 4 is a schematic diagram of a preferred embodiment of a controldevice included in the power control system of FIG. 1, FIG. 2, or FIG.3.

FIG. 5 is a schematic diagram of a preferred embodiment of a controldevice included in the power control system of FIG. 1, FIG. 2, or FIG.3, further operating as a voltage regulator.

FIG. 6 is a schematic diagram of a preferred embodiment of a controldevice included in the power control system of FIG. 1, FIG. 2, or FIG.3, further operating as a voltage regulator.

FIG. 7A is a flow diagram of one preferred method of operation of thepower control system of FIG. 1, FIG. 2, or FIG. 3.

FIG. 7B is a diagram of one preferred method of applying a phasemodulated signal corresponding to FIG. 7A.

FIG. 8A is a flow diagram of one preferred method of operation of thepower control system of FIG. 1, FIG. 2, or FIG. 3, further operating asa voltage regulator.

FIG. 8B is a diagram of one preferred method of applying a phasemodulated signal corresponding to FIG. 8A.

FIG. 9A is a flow diagram of one preferred method of operation of thepower control system of FIG. 1, FIG. 2, or FIG. 3, further operating asa voltage regulator.

FIG. 9B is a diagram of one preferred method of varying a regulationvoltage corresponding to FIG. 9A.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 depicts a block diagram of a preferred embodiment of a powercontrol system 100, including a generator 102, a prime mover 122, anaccessory 124, and a control device 108. The control device 108 isconnected to and in communication with the generator 102 via a generatorspeed indicator 104 and a generator output power controller 106. Thecontrol device 108 ascertains a change in speed of the generator bymeasuring a change between two consecutive speeds of the generator speedindicator 104 via a line 134. The control device 108 varies an outputpower of the generator 102 by applying a signal to the generator outputpower controller 106 via a line 110. It should be clear to a skilledartisan that the term signal, as used throughout this specificationincluding the drawings, refers to both analog and digital signal whethertransmitted through wire or wireless. The control device 108 is poweredby the output of the generator 102 via a line 112. The generator 102 iscoupled with and driven by the prime mover 122 via a coupling mechanism128 that imparts a rotational speed of a shaft 130 of the prime mover122 on a shaft 126 of the generator 102. The generator 102 convertsmechanical power of the prime mover 122 into electrical power which isavailable to a variable electrical load 114. The variable electricalload 114 represents electrical loads by electrical components which maycomprise a battery, a heating element, an air conditioning unit, acompressor, a cooling fan, or a pump, to name a few examples. As theseelectrical loads are applied and removed from the generator 102, theprime mover 122 experiences the corresponding mechanical loads whichcause the rotational speed of the prime mover 106 to vary, accordingly.The prime mover 122 is further coupled with and drives an accessory 124such as an electrical motor. The mechanical load of the accessory 124 onthe prime mover 122 further varies the rotational speed of the latter.In one embodiment, the control device 108 may be configured to furtheroperate as a voltage regulator by sensing an output voltage of thegenerator 102, via the line 112, and maintaining the output voltage at aregulation voltage, via the line 110, The control device 108 furthercomprises a sensor 120 capable of measuring a temperature wherein thecontrol device 108 may vary the regulation voltage according to thetemperature. The control device 108 further comprises a light emittingdiodes (LED) 116 and an I/O port 118 to communicate system information.

In one embodiment, the prime mover 122 is an internal combustion engine,the generator 102 is an alternator, and the coupling mechanism 128 is adrive belt. The internal combustion engine drives the alternator via thedrive belt. The generator output power controller 106 is a field coiland the generator speed indicator 104 is a phase winding of thealternator. The line 134 is connected to the phase winding and operativeto sense an oscillating voltage proportional to the rotational speed ofthe shaft 126 of the alternator. The line 110 is connected to the fieldcoil and operative to apply a control signal to the latter therebyvarying the output power of the alternator. In this embodiment, thecontrol device 108 measures a change in the rotational speed bydetermining a difference between two consecutive rotational speed valuesω₁ and ω₂, sampled a pre-determined time interval apart. When the changeis above a threshold, the control device 108 applies a speed-controlsignal to the field coil via the line 110 to vary the output power ofthe alternator. In one instance, the speed-control signal comprises aphase modulated signal causing the average field current to decreasewhen the change is negative, i.e., the rotational speed of thealternator is decreasing. In another instance, the speed-control signalcomprises a step signal causing the average field current to increasewhen the change is positive, i.e., the speed is increasing.

As stated above, the change in the RPM can have a negative or a positivesign. A negative sign indicates that the engine rotational speed isdecreasing and a positive sign indicates that the engine's RPM isincreasing. A decreasing RPM can lead to engine stall or other undesiredeffects on the engine, and an increasing RPM may signify a suddenavailability of engine power. In either case, the change can be comparedwith one or more threshold values to apply an appropriate controlsignal.

For instance, the system can be configured so that changes in speed,either positive or negative, below a threshold value are ignored,signifying that such changes are within normal operating conditions. Onthe other hand, speed changes at or above the threshold are acted uponsignifying that the system requires adjustments. The change can becompared with a threshold value R_(C). If the change is at or above thisvalue, a second comparison is performed with respect to the algebraicsign of the change. If the change is negative, i.e., the speed isdecreasing, the control device 108 applies a phase modulated signal,causing the generator output power controller 106 to attenuate thegenerator output power. If the change is positive, the control device108 applies a step signal, causing the generator output power controller106 to switch on, thereby restoring the generator output power.

It should be clear to a skilled artisan that the generator output powercontroller 106 can be a passive or an active component. This means thatin the present embodiment, the generator output power controller 106(the field coil) is a passive component, to the extent that the outputpower of the generator 102 is controlled by a voltage regulator (notshown) via the field coil. In another embodiment, the generator outputpower controller 104 is an active component, to the extent that itactively controls the generator output power. A voltage regulator (notshown) capable of controlling the generator output power by controllingthe field current can be utilized. In the former case, the controldevice 108 applies a control signal to the field coil directly whichoverrides any other control signal acting upon the field coil by thevoltage regulator. In the latter case, the control device 108 applies acontrol signal to the voltage regulator directly causing the voltageregulator to apply the control signal generated by the control device108 over any other control signal generated by the voltage regulator.Two variations of this embodiment will be discussed in more detailbelow. In either case, the control device 108 applies a control signalto the generator output power controller 106 to vary the output power ofthe generator 102 according to a change in speed, and such controlsignal overrides any other control signal operating to control thegenerator output power until changes in speed fall within normaloperating conditions, and the control device 108 relinquishes control ofthe otherwise normal generator output power. It is contemplated that inother embodiments, the generator 102 and the control device 108 are eachequipped with a wireless transmitter/receiver (not shown but known toskilled artisans) that can replace the line 134 and line 110, whereinthe generator 102 transmits the rotational speed of the generator whichthe control device 108 receives to measure a change, and wherein thecontrol device 108 transmits a control signal which the generator 102receives to vary its output power according to the change.

In one embodiment, the control device 108 comprises a voltage regulator(discussed below) that maintains the output voltage of the generator 102at a regulation voltage, for instance 28 Volts. The control device 108achieves this by sensing the output voltage of the generator 102 bymeasuring a voltage of the line 112 and switching on/off the field coilvia the line 110 to maintain the output voltage substantially at theregulation voltage. According to this embodiment, the control device 108operates to control the generator output power at all times includingthose when the change in speed is below any event-specific threshold. Ina variation of the present embodiment, the sensor 120 is utilized tomeasure a temperature, for example the temperature of a battery (notshown), and vary the regulation voltage according to the temperature.

According to another embodiment, the generator 102 is a permanent magnetalternator, the prime mover 122 is a pneumatic or fluid powered engine,and the coupling mechanism 128 is a direct drive coupling. In oneconfiguration, the alternator shaft 126 is mated with a drive couplingof shaft 130. The generator output power controller 106 is a siliconcontrolled rectifier (SCR) and the generator speed indicator 104 is atachometer. The control device 108 senses a rotational speed of thealternator via the line 134 and applies a control signal according to ameasured change in the speed, via the line 110, operative to vary theoutput power of the alternator.

It should be clear to a skilled artisan that the generator output powercontroller 106 can be a passive or an active component. This means thatin the present embodiment, the generator output power controller 106(the SCR) is a passive component, to the extent that the output power ofthe generator 102 is controlled by a voltage regulator (not shown) viathe SCR. In another embodiment, the generator output power controller106 is an active component, to the extent that it actively controls thegenerator output power. A voltage regulator (not shown) capable ofproviding a signal indicative of the field coil duty cycle can beutilized. A voltage regulator (not shown) capable of controlling thegenerator output power by switching on/off the SCR can be utilized. Inthe former case, the control device 108 applies a control signal to theSCR directly which overrides any other control signal acting upon theSCR by the voltage regulator. In the latter case, the control device 108applies a control signal to the voltage regulator directly causing thevoltage regulator to apply the control signal generated by the controldevice 108 over any other control signal generated by the voltageregulator. In either case, the control device 108 applies a controlsignal to the generator output power controller 106 to vary the outputpower of the generator 102 according to a change in speed, and suchcontrol signal overrides any other control signal operating to controlthe generator output power until changes in speed fall within normaloperating conditions, and the control device 108 relinquishes control ofthe otherwise normal generator output power.

FIG. 2 depicts a block diagram of a preferred embodiment of a powercontrol system 200, including a prime mover 122, generator 102,accessory 124, control device 206, and transmission 208. Thisconfiguration is well adapted for applications in motor vehicles, wherethe prime mover 122 is an internal combustion engine and thetransmission 208 is coupled to the engine via a coupling mechanism 212and utilized to propel the vehicle. In this embodiment, the generator102 is coupled with the engine via a coupling mechanism 128. The controldevice 206 is connected to and in communication with the generator 102in a similar manner as shown in FIG. 1. In this embodiment, the controldevice 206 is configured to measure a change in generator RPM via theline 134 and apply a control signal to the generator output powercontroller 106, via the line 110, according to the change. According tothis embodiment, the control device 206 controls the generator outputpower at all times regardless of the state of the transmission 208. Inanother embodiment, the control device 206 may be connected to and incommunication with the transmission 208 via a line 210 to monitor thestate of the transmission 208, and become operative only when thetransmission state is set to specific states, for example neutral orparked.

For instance, in a vehicle application, the transmission 208 is engagedby the vehicle operator to propel the vehicle. During the period whenthe transmission 208 is so engaged, the control device 206 is signaled,via the line 210, that the generator output power should not becontrolled based on a change in generator speed. When the vehicleoperator sets the transmission 208 to either a neutral or parked state,the control device 206 senses this condition via the line 210 andcommences to vary the output power of the generator according to themeasured change in the rotational speed of the generator 102. In anotherinstance, in a vehicle application, the control device 206 may beconfigured to control the generator output power regardless of the stateof the transmission 208. Accordingly, acceleration and deceleration ofthe vehicle engine cause the control device 206 to control the generatoroutput power based on a change in RPM as described above.

FIG. 3 depicts a block diagram of a preferred embodiment of a powercontrol system 300, including a prime mover 122, generator 102,accessory 124, control device 324, and output speed converter 320. Thecontrol device 324 is connected to and in communication with thegenerator 102 in a similar manner as shown in FIG. 1. The output speedconverter 320 is coupled with the prime mover 122, via a couplingmechanism 312, and the generator 102, via a coupling mechanism 306. Thecontrol device 324 is configured to measure a change in the generatorspeed, via the line 134 and apply a control signal to the generatoroutput power controller 106 via the line 110 according to the change.

An example of the present embodiment is where the prime mover 122 is aturbine engine and the output speed converter 320 is a power train thatconverts a rotational speed of an output shaft 310 of the turbine engineto a variable speed of the power train. An input shaft 308 of the outputspeed converter 320 is coupled with the output shaft 310 of the turbineengine via the coupling mechanism 312, for instance a direct drivecoupling of the type discussed above, and rotates at the same speed asthe turbine engine output shaft 310. An output shaft 304 of the outputspeed converter 320 is coupled with a shaft 302 of the generator 102 viathe coupling 306 which may be a direct drive coupling of the typediscussed above. As the speed of the output speed converter 320 changes,the control device 324 measures a change in the rotational speed of thegenerator 102, via the first line 134, and applies a control signal, viathe line 110, to vary the output power of the generator 102 according tothe change.

FIG. 4 depicts a schematic diagram of a preferred embodiment of acontrol device 400 as an electrical circuit. In this embodiment, thecontrol device comprises a processor 406. The processor 406 preferablycomprises a microprocessor, a processor clock, and a power supply. Inone preferred embodiment, the microprocessor is a 68C08 processor havinginternal flash memory available from Motorola, Inc. of Schaumburg, Ill.The internal clock may be a crystal-type oscillator or other oscillatormechanism known to those practiced in the art, and the power supply maybe a discrete or integrated circuit configured to supply the processor406 with appropriate DC voltage. It is contemplated that the processormay be a combination of individual discrete or separate integratedcircuits packaged in a single housing or it may be fabricated in asingle integrated circuit.

The processor 406 is connected to and in communication with a generator(not shown) via a connector 402. The processor 406 is further connectedto and in communication with MOSFETS 412, 414, 416, and 418 wherein theprocessor 406 may regulate an output voltage of the generator at aregulation voltage. It should be clear to a skilled artisan that whenthe control device is operating to control the generator output poweronly in response to a change in speed of the generator, only the MOSFET412 is required to perform the task. When the control device operatesfurther to regulate the output voltage one or more of the MOSFETS 412thru 418 may be utilized to perform the task. Two different embodimentsof the control device further operating as a voltage regulator will bediscussed below, wherein one embodiment the control device utilizes twoseparate MOSFETS such as the MOSFETS 412 and 416, and wherein the otherembodiment the control device utilizes a single MOSFET such as theMOSFET 412. Utilization of the other two MOSFETS 414 and 418 is toprovide redundant and over voltage protection as discussed below. Theprocessor 406 is further connected to and in communication with atemperature sensor and an I/O port via connectors 404 and 410,respectively.

In one embodiment, the connector 402 comprises four separate terminals,namely an ALT terminal 442, an F-terminal 444, an AC terminal 446, and aGND terminal 448. Preferably, the ALT terminal 442 is used to couple toan output terminal of the generator via a line 452, the F-terminal 444is used to couple with an output power controller of the generator, forinstance, a field coil via a line 454, the AC terminal 446 is used tocouple with a phase terminal of the generator via a line 456, and theGND terminal 448 is used to couple with a ground terminal via a line458, providing a return path for the current flow. Preferably, theprocessor 406 utilizes: (1) the ALT terminal 442 to measure an outputvoltage of the generator, (2) the F-terminal 444 to vary the generatoroutput power, (3) the AC terminal 446 to ascertain a change in thegenerator speed, and (4) the GND terminal 448 to access a groundterminal.

In one embodiment, the connector 450 is utilized to connect to andcommunicate with the transmission. Preferably, the P1 terminal 428 isutilized to couple with the transmission via a line 460.

In one embodiment, the processor 406 connects to and communicates withMOSFETS 412, 414, 416, and 418, via lines 488, 490, 492, 494, 496, and458. Preferably, MOSFETS 412 and 414 are coupled in a parallelconfiguration and are utilized to regulate an output voltage of thegenerator at a regulation voltage, for instance 28 V, and MOSFETS 416and 418 are also coupled in a parallel configuration, and are utilizedto protect the generator from excessive voltage, for instance, 30 V acondition commonly referred to as an over voltage cut off (OVCO)condition. Other transistors instead of the MOSFETS may be utilized toperform the same task as known by skilled artisans Furthermore, itshould be clear to a skilled artisan that a single transistor can beused to regulate the voltage and that multiple transistors are used hereto provide redundant and OVCO protection.

In one embodiment, the processor 406 connects to and communicates with atemperature sensor (not shown) via a terminal 470 of the connector 404.Preferably, the processor 406 utilizes a line 472 to measure atemperature, for instance an ambient temperature, to compensate theregulation voltage accordingly. In another embodiment, the processor 406connects to and communicates with a computer system via a CAN-L terminal476, CAN-H terminal 478, and GND terminal 480 of the connector 410.Preferably, the processor 406 utilizes lines 482, 484, and 486 totransmit/receive system information. In one variation of the presentembodiment, the processor 406 utilizes a CAN Protocol to exchange systeminformation.

Referring to FIG. 4 and utilizing FIG. 5 and FIG. 6, two embodiments ofthe control device 400 are discussed where the control device 400further operates as a voltage regulator. In both embodiments, thecontrol device 400 operates to control the generator output power basedon generator output voltage and changes in generator RPM. Consequently,a generator, included in a power conversion system such as thosedepicted in FIG. 1, FIG. 2, or FIG. 3, can be controlled not only basedon its output power capacity, but also how its output power affects thepower conversion system.

In FIG. 5, a microprocessor 500 is connected with a generator speedindicator 504, via a line 502, with a generator output power controller518, via a line 522, and with a generator output terminal 520, via aline 524. The generator speed indicator 504 may be a tachometer or agenerator phase winding. The generator output power controller may be afield coil or an SCR. The microprocessor 500 is configured to regulatean output voltage of the generator (not shown) at a regulation voltageV_(R), by switching on/off an output voltage responsive switch 514, suchas MOSFET 412, shown in FIG. 4.

Under normal operating conditions, i.e., speed changes less than athreshold value R_(C), the microprocessor 500 switches on/off the outputvoltage responsive switch 514, via a line 506, to maintain the outputvoltage of the generator at the regulation voltage V_(R), and keeps anRPM responsive switch 510 switched on, via a line 508. When a change inspeed is at or above the threshold value R_(C), the microprocessor 500applies a control signal to the RPM responsive switch 510, via the line508. If the change is negative, i.e., the RPM is decreasing, themicroprocessor 500 applies a phase modulated signal to the RPMresponsive switch 510, via the line 508, to reduce the generator outputpower. If the change is positive, i.e., the RPM is increasing, themicroprocessor 500 applies a step signal to the RPM responsive switch510, via the line 508, to restore the generator output power.

In FIG. 6, a microprocessor 600 is connected with a generator speedindicator 604, via a line 602, with a generator output power controller616, via a line 612, and with a generator output terminal 614, via aline 618. The generator speed indicator 604 may be a tachometer or agenerator phase winding. The generator output power controller may be afield coil or an SCR. The microprocessor 600 is configured to regulatean output voltage of the generator (not shown) at a regulation voltageV_(R), by switching on/off an RPM/Output voltage responsive switch 608,such as MOSFET 412, shown in FIG. 4. This embodiment differs from thatdepicted in FIG. 5 in that a single switch can be utilized to controlthe generator output power based on generator output voltage and speed.

Under normal operating conditions, i.e., speed changes less than athreshold value R_(C), the microprocessor 600 switches on/off theRPM/Output voltage responsive switch 608, via a line 606, to maintainthe output voltage of the generator at the regulation voltage V_(R).When a change in speed is at or above the threshold value R_(C), themicroprocessor varies the regulation voltage V_(R) according to thechange. If the change is negative, i.e., the RPM is decreasing, themicroprocessor 600 reduces the regulation voltage V_(R). If the changeis positive, i.e., the RPM is increasing, the microprocessor 600restores the regulation voltage V_(R).

Utilizing the system 100 described in FIG. 1, one embodiment of theoperation of the control device 108 is now described. The generator 102is a permanent magnet alternator having an SCR as an output powercontroller 106 and the prime mover 122 is an internal combustion engine.The control device 108 ascertains a change in the speed of thealternator via the generator speed indicator 104 and varies an outputpower of the generator according to the change. This embodiment mayreadily be implemented in a generator set available from C. E. Niehoff&Co., Evanston, Ill.

In one situation, the control device 108 senses a voltage variation froma signal received via the line 134. A processor, such as the processor406 depicted in FIG. 4 and included in the control device 108,calculates a change in the RPM (as described above), utilizing anonboard programming code stored in the memory of the processor 406. Thischange is compared with a threshold value R_(C). If the absolute valueof the change is less than R_(C), the processor 406 does not change thegenerator output power. When the change is at or above R_(C), thecontrol device 108 applies a control signal to the generator outputpower controller 106, via the line 110, to either reduce or restore thegenerator output power. When the algebraic sign of the change isnegative, i.e., the speed is decreasing, the control device 108 appliesa control signal, such as a phase modulated signal, to the generatoroutput power controller 106 to attenuate the generator output power.When the algebraic sign of the change is positive, i.e., the speed isincreasing, the control device 108 applies a control signal, such as astep signal, to the generator output power controller 106 to restore thegenerator output power.

In one embodiment, the above control device 108 may further operate toregulate the output voltage of the generator 102. Referring to FIG. 5,the processor 500 senses a signal, via the line 502, from the generatorspeed indicator 504, say a phase winding of the generator 102, tomeasure a change in speed of the generator 102. The processor 500further senses a signal, via the line 524, from the generator outputterminal 520, to measure an output voltage of the generator 102. Theprocessor 500 applies a voltage-control signal to the output voltageresponsive switch 514, via the line 506, to regulate the output voltageof the generator 102 at a regulation voltage V_(R). The processor 500applies a speed-control signal to the RPM responsive switch 510, via theline 508, if a change in speed is at or above a threshold value R_(C).Accordingly, the control device 108 controls the output power of thegenerator 102 based on change in speed and output voltage of thegenerator 102.

Utilizing the system 200 described in FIG. 2, one embodiment of theoperation of the control device 206 is now described. The generator 102is a brushless alternator having a field coil as an output powercontroller 106, available from C.E. Niehoff & Co. of Evanston, Ill. Theprime mover 122 is an internal combustion engine. The transmission 208is engaged via a transmission control module (not shown but known toskilled artisans). The control device 206 ascertains a change in therotational speed of the alternator and varies an output power of thealternator according to the change when the transmission control moduleis set to either a neutral or parked position. This embodiment mayreadily be implemented in a motor vehicle.

In one situation, the system 200 is utilized to power and propel thevehicle, utilizing the engine and transmission, and provide electricalpower to the vehicle accessories, represented by the variable load 114,utilizing the alternator. The mechanical load imparted on the engine bythe accessory 124 is representative of other mechanical loads on theengine. The control device 206 monitors a signal via the line 210 todetermine the state of the transmission 208. When the vehicle operatorsets said state to either neutral or parked, the control devicecommences to control the output power of the alternator. A processor,such as the processor 406 depicted in FIG. 4 and included in the controldevice 206, calculates a change in the RPM (as described above),utilizing an onboard programming code stored in the memory of theprocessor 406. As described above, this change is compared with athreshold value R_(C) and an appropriate control signal is applied tothe generator output power controller 106 to control the generatoroutput power controller.

In one embodiment, the control device 206 may further operate toregulate the output voltage of the generator 102. Referring to FIG. 6,the processor 600 senses a signal, via the line 602, from the generatorspeed indicator 604 to measure a change in the generator speed. Theprocessor 600 further senses a signal, via the line 618, from thegenerator output terminal 614, to measure an output voltage of thegenerator 102. The processor 600 applies a voltage-control signal to theRPM/Output voltage responsive switch 608, via the line 606, to regulatethe output voltage of the generator 102 at a regulation voltage V_(R),for instance 14 V. The processor 600 varies the regulation voltage V_(R)if a change in speed is at or above a threshold value R_(C). If thealgebraic sign of the change is negative, the processor 600 reduces theregulation voltage V_(R), and if the algebraic sign of the change ispositive, the processor 600 restores the regulation voltage V_(R).Accordingly, the control device 206 controls the output power of thegenerator 102 based on change in speed and output voltage of thegenerator 102.

In another situation, the system 200 may readily be used when the stateof the transmission 208 is set to drive condition. According to thisembodiment, the control device 206 senses a rotational speed of thealternator and varies the generator output power when a change in theRPM is at or above a threshold value R_(C), as described above. In onevariation of the present embodiment, the processor 406 may be configured(programmed) to cyclically measure the change and control the generatoroutput power according to the change. In another variation, a specialpurpose integrated circuit may be configured to interrupt (hardwareinterrupt) the processor 406 when a change is at or above the thresholdvalue R_(C). Consequently, there are no preferences given to the stateof the transmission 208 and the present invention can be implemented ina vehicle throughout all operating conditions.

Utilizing the system 300 described in FIG. 3, one embodiment of theoperation of the control device 324 is now described. The generator 102is a brushless alternator having a field coil as an output powercontroller 106. The prime mover 122 is a turbine engine. The outputspeed converter 320 is a power train that is coupled with the engine andthe alternator. The power train operates to convert a rotational speedof the turbine output shaft. The control device 324 ascertains a changein the rotational speed of the alternator and varies the output power ofthe alternator according to the change. This embodiment may readily beimplemented in an aircraft.

In one embodiment, as described above, the control device 324, operatesto control the generator output power based on change in speed only. Inanother embodiment, as described above, where the control device 324further operates as a voltage regulator, the control device 324 controlsthe generator output power based on both the change in speed and outputvoltage of the generator 102. As described above, two differentimplementations can be utilized according to FIG. 5 and FIG. 6. In theformer, FIG. 5, two separate switches are utilized, one to control thegenerator output power according to the changes in speed of thegenerator, and the other to control the generator output power based onthe generator output voltage. In the latter, FIG. 6, one switch isutilized to control the generator output power based on change in speedand output voltage, by varying the regulation voltage V_(R) as describedabove.

FIGS. 7A and 7B illustrate an example of one method of operating thecontrol device 108, utilizing FIGS. 1 and 4, where the control device108 operates to control the output power of the generator 102 based onlyon changes in the generator speed. Upon power up at 700, the processor406 measures a change in speed (R), at 704, of the generator 102, viathe line 134. The absolute value of the change (R) is then compared to athreshold value R_(C) at 708. If this value is less than the thresholdvalue R_(C), the processor 406 will not affect the generator outputpower, branching at 724 to continue measuring a change (R) in the speedof the generator 102. If, however, the absolute value of the change (R)is at or above the threshold value R_(C), the processor 406 branches at710 and performs a comparison on the algebraic sign of the change (R) at712. If the change (R) is negative, the processor 406 branches at 714and operates to reduce the generator output power by applying a phasemodulated signal to the MOSFET 412 with duty cycle (D) at 716. In onevariation of the present embodiment, the processor 406 uses a look uptable, stored in the memory of the processor 406, as depicted in FIG.7B. The look up table is utilized to relate the duty cycle (D) to thechange (R), at 728. The processor 406 branches at 722 to continuemeasuring a change (R) in the speed of the generator 102. If the change(R) is positive, the processor 406 branches at 718 and operates torestore the generator output power by applying a step signal to theMOSFET 412 at 720. In one variation, the step signal is a signal thatswitches on the MOSFET 412. The processor 406 branches at 726 tocontinue measuring a change (R) in the speed of the generator 102.

FIGS. 8A and 8B illustrate an example of one method of operating thecontrol device 108, utilizing FIGS. 2 and 5, where the control device108 operates to control the output power of the generator 102 based onboth changes in the generator speed and generator output voltage. Uponpower up at 800, the processor 500 regulates the generator outputvoltage at 804 at a regulation voltage V_(R) by sensing an outputvoltage of the generator via the line 524. The regulation is performedby the output voltage responsive switch 514, as described above. Theprocessor 500 branches at 806 to measure a change in speed (R) of thegenerator 102, at 808, via the line 502, which is coupled with thegenerator speed indicator 504. The absolute value of the change (R) isthen compared to a threshold value R_(C) at 812. If this value is lessthan the threshold value R_(C), the processor 500 will not affect thegenerator output power, branching at 828 to continue regulating thegenerator output voltage. If, however, the absolute value of the change(R) is at or above the threshold value R_(C), the processor 500 branchesat 814 and performs a comparison on the algebraic sign of the change (R)at 816. If the change (R) is negative, the processor 500 branches at 818and operates to reduce the generator output power by applying a phasemodulated signal to RPM responsive switch 510 with duty cycle (D) at820. In one variation of the present embodiment, the processor 500 usesa look up table, stored in its memory, as depicted in FIG. 8B. The lookup table is utilized to relate the duty cycle (D) to the change (R), at832. The processor 500 branches at 824 to continue regulating thegenerator output voltage. If the change (R) is positive, the processor500 branches at 822 and operates to restore the generator output powerby applying a step signal to RPM responsive switch 510 at 826. Theprocessor 500 branches at 830 to continue regulating the generatoroutput voltage.

FIGS. 9A and 9B illustrate an example of one method of operating thecontrol device 108, utilizing FIGS. 3 and 6, where the control device108 operates to control the output power of the generator 102 based onboth changes in the generator speed and generator output voltage. Uponpower up at 900, the processor 600 regulates the generator outputvoltage at a regulation voltage V_(R) at 904 by sensing an outputvoltage of the generator via the line 618. The regulation is performedby the RPM/Output voltage responsive switch 608, as described above. Theprocessor 600 branches at 906 to measure a change in speed (R) of thegenerator 102, at 908, via the line 602, which is coupled with thegenerator speed indicator 604. The absolute value of the change (R) isthen compared to a threshold value R_(C) at 912. If this value is lessthan the threshold value R_(C), the processor 600 will not affect thegenerator output power, branching at 928 to continue regulating thegenerator output voltage. If, however, the absolute value of the change(R) is at or above the threshold value R_(C), the processor 600 branchesat 914 and performs a comparison on the algebraic sign of the change (R)at 916. If the change (R) is negative, the processor 600 branches at 918and operates to reduce the generator output power by reducing theregulation voltage V_(R) at 920. In one variation of the presentembodiment, the processor 600 uses a look up table, stored in itsmemory, as depicted in FIG. 9B. The look up table is utilized to relatethe amount of reduction in the regulation voltage V_(R) to the change(R), at 932. The processor 600 branches at 924 to continue regulatingthe generator output voltage. If the change (R) is positive, theprocessor 600 branches at 922 and operates to restore the generatoroutput power by restoring the regulation voltage V_(R) at 926. Theprocessor 600 branches at 930 to continue regulating the generatoroutput voltage.

In FIGS. 7A thru 9B, the processor may be configured to communicate oneor more system status via an LED 116 or an I/O port 118, as depicted inFIG. 1, following applying the appropriate control signal. It should beclear to a skilled artisan that the program included in the processormay operate to regulate the generator output voltage concurrently withmeasuring the change in generator speed. As described above, the changemeasurements can either be performed cyclically or interrupt driven.

The forgoing discloses a power control system comprising a controldevice, a prime mover, and a generator. The prime mover drives thegenerator and the control device ascertains a change in speed of thegenerator and varies an output power of the generator according to thechange. The system may include a transmission where the control deviceoperation is conditioned on whether the transmission is in a particularstate, or regardless of the state of the transmission. The system mayinclude a speed converter coupled with the prime mover wherein thecontrol device operates to vary the generator output power according toa change in speed of the generator. The control device may also operateto control an output power of the generator, for instance, operate toregulate an output voltage of the generator.

The foregoing explanations, descriptions, illustrations, examples, anddiscussions have been set forth to assist the reader with understandingthis invention and further to demonstrate the utility and novelty of itand are by no means restrictive of the scope of the invention. It is thefollowing claims, including all equivalents, which are intended todefine the scope of this invention.

1. A control device for a generator driven by a speed converter, said speed converter coupled with the generator and a prime mover and capable of converting a speed of the prime mover, said generator comprising a generator output power controller capable of manipulating an output power of the generator and a generator speed indicator capable of generating a signal indicative of the generator speed, said control device comprising: a processor, including a programming code operable on the processor, coupled with the generator output power controller and the generator speed indicator; wherein said processor is configured to measure a rate of change in speed of the generator, via a first line, and to vary the output power of the generator by applying a speed-control signal to the generator output power controller, via a second line, according to said rate of change.
 2. A method for controlling a generator driven by a speed converter, said speed converter coupled with the generator and a prime mover and capable of converting a speed of the prime mover, said generator comprising a generator output power controller capable of manipulating an output power of the generator and a generator speed indicator capable of generating a signal indicative of the generator speed, said method comprising: (a) measuring a rate of change in speed of the generator, via a first line; and (b) varying the output power of the generator by applying a speed-control signal to the generator output power controller, via a second line, according to said rate of change. 